The invention relates to an apparatus for controlling an air actuated governor that controls the speed of an engine in a vehicle. The governor is designed to allow the engine to operate up to a preselected maximum rpm when air under pressure is supplied to the governor and at a lower maximum rpm when the supply of air to the governor is interrupted. This invention is particularly designed for use on a transmission having a splitter gear incorporated as part of the transmission. In one of the more specific aspects of the present invention, the manual shift rod in the transmission and the splitter shift rod must be in alignment in the selected gear to disrupt the flow of air under pressure to the governor to change the maximum rpm setting in the governor.
Air controlled speed governors have been used on engines for industrial and commercial vehicles for a number of years. The speed governors are actuated by air under pressure that is supplied to the governor. The pressurized air actuates the governor and allows the engine of the vehicle to accelerate until a maximum rpm for the engine is obtained. Normally a maximum rpm in the range of 2100 to 2600 rpm is desirable for a commercial or industrial diesel powered vehicle. The operator of the vehicle, will shift through the gears in the transmission of the vehicle until the desired operating speed is reached. Normally the vehicle is held in a particular gear until the maximum rpm level for the engine is reached and then the transmission is shifted into the next gear. This gear shifting process is repeated until the desired operating speed is achieved. During the shifting of the vehicle, air under pressure is supplied to the governor and the engine is free to accelerate up to the maximum rpm level.
However, on a number of vehicles it is desirable to limit the maximum rpm in the highest gear of the transmission to keep the vehicle from exceeding the maximum speed allowed on the nation's highways. It is also frequently desirable to limit the maximum rpm in high gear to keep the engine operating in its most efficient rpm range during extended use on the highway. Accordingly, the air actuated governor is designed to limit the maximum rpm at which the engine can operate to a predetermined level when the supply of air under pressure to the governor is interrupted. This preselected maximum rpm level normally corresponds with an rpm level that is at or about the maximum legal speed or approximates the most effective rpm range at which the engine can be operated
It is usually desirable to reduce the maximum rpm setting of the governor in only certain gears of the transmission and usually only in the highest gear of the transmission. This is because the vehicle will normally be in this highest gear during most of its operation on the highway. It is more important for the engine to be operating at its maximum efficiency during this mode of operation. In addition, it is also frequently necessary to have additional power available in the lower gears to allow the vehicle to accelerate and operate effectively when fully loaded. Therefore, it is important to allow the engine to accelerate to the maximum rpm level in these lower gears to provide additional power and acceleration for the vehicle.
Further, the limitations on the maximum engine rpm to stay within the maximum legal speed are not as significant in the lower gears. In these lower gears the vehicle is usually not capable of obtaining the maximum legal highway speed. Therefore if it is desirable to restrict the maximum speed of the vehicle to approximately the maximum legal speed it is usually only necessary to alter the maximum rpm setting of the governor in the highest gear for the transmission.
A number of transmission used for industrial and commercial applications contain a splitter gear which effectively doubles the number of gears present in the transmission. In a transmission with a splitter gear the transmission is manually shifted into the highest manually selected gear and the splitter gear is engaged to obtain the highest gear in the transmission. Therefore, in a transmission with a splitter it is necessary to coordinate the position of the manually shifted gears and the splitter gear to determine when the transmission is in top gear to disrupt the flow or pressurized air to the governor to reduce the maximum permissible engine rpm.
Accordingly, there is a need in the industrial and commercial vehicle field for a device to determine the position of the manually selected gears and the splitter gear in a transmission. The device should be capable, when the manually selected gears and splitter gear are in the preselected position, of causing the interruption of the flow of pressurized air to the governor on the engine on the vehicle to reduce the maximum permissible engine rpm.